Optical Networks - Tutorialspoint
Optical Networks
Optical NetworksAbout the TutorialOptical networks are telecommunications network of high capacity. They are based onoptical technologies and components, and are used to route, groom, and restorewavelength levels and wavelength-based services.This tutorial is divided into distinct chapters, which explains the structural features ofoptical fibers and their connections in networks. The nature of optical networks along withthe recent developments in the Optical and Networking systems using optical sources anddevices is also dealt with.AudienceThis tutorial is designed for learners who have interest in learning the networking conceptsusing optical sources. It will be useful for those having some idea regarding networkingand optical sources.PrerequisitesReaders will benefit from this tutorial if they are aware of basic networking concepts. Afair idea on digital networking and digital communication systems will be a plus.Copyright & Disclaimer Copyright 2017 by Tutorials Point (I) Pvt. Ltd.All the content and graphics published in this e-book are the property of Tutorials Point (I)Pvt. Ltd. The user of this e-book is prohibited to reuse, retain, copy, distribute or republishany contents or a part of contents of this e-book in any manner without written consentof the publisher.We strive to update the contents of our website and tutorials as timely and as precisely aspossible, however, the contents may contain inaccuracies or errors. Tutorials Point (I) Pvt.Ltd. provides no guarantee regarding the accuracy, timeliness or completeness of ourwebsite or its contents including this tutorial. If you discover any errors on our website orin this tutorial, please notify us at contact@tutorialspoint.comi
Optical NetworksTable of ContentsAbout the Tutorial . iAudience . iPrerequisites . iCopyright & Disclaimer . iTable of Contents . ii1.OPTICAL NETWORKS INTRODUCTION . 12.OPTICAL NETWORKS CONVERGENCE NETWORKS . 2Optical Transport Networking: A Practical View . 3Client Signal Transparency . 4Optical Transport Networking via Digital Wrappers . 5Protocol Stack Choices . 7What is IP over WDM? . 83.OPTICAL NETWORKS OPTICAL DATA NETWORKING. 9Transponder (TP). 10Variable Optical Attenuator (VOA) . 11Multiplexer (MUX) and Demultiplexer (De-MUX). 11Types of Multiplexer/ Demultiplexer . 12Booster Amplifiers (Optical Amplifiers) . 14Types of Optical Amplifiers . 15Line Amplifiers . 16Line (OFC) Media . 16Pre-Amplifier (PA) . 16Optical Supervisory Channel . 16ii
Optical Networks4.OPTICAL NETWORKS – OPTICAL DEVICES . 17Isolator . 17Circulator . 17Splitters & Couplers . 18Filters . 19Modulators . 19Optical ADM . 20Optical Cross-Connect . 215.OPTICAL NETWORKS - SINGLE & MULTI-HOP NETWORKS . 22Synchronous Digital Hierarchy . 22SDH - Network Topologies . 23Ring System. 23SDH Network Synchronization . 24SDH Hierarchy . 256.OPTICAL NETWORKS - WDM TECHNOLOGY. 26WDM in the Long Haul . 26WDM in the Short Haul . 29Optical Transport Network Architectures . 30Optical Layer Survivability . 31Why Optical Layer Protection? . 33Limitations - Optical Layer Protection . 34Definitions of Protected Entities . 35Protection Vs Restoration . 36Sublayers Within the Optical Layer . 36Line Layer versus Path Layer Protection . 40Client Protection . 40iii
Optical NetworksPath Layer Schemes . 41Line Layer Schemes . 42Consideration for the Choice of Protection Scheme . 43The Cost of Protection . 437.OPTICAL NETWORKS ROADM . 45Reconfigurable WDM Network with ROADMs . 46Simplifications Through ROADMs. 47ROADM Architecture. 47The ROADM Heart – the WSS Module . 48ROADM – Degrees, Colorless, Directionless, and More . 49iv
1.Optical NetworksOptical Networks IntroductionThe current thinking about IP over WDM by outlining a path to optical data networking,that includes multiple data networking protocol coupled with a protocol-neutral opticalnetworking infrastructure is challenged. This tutorial discusses the diversity of datanetworking protocols and network architectures for optical data networking.The bandwidth explosion ushered in by the popularity of the Internet has led to a paradigmshift in the telecommunication industry from voice-optimized circuit-switched services todata-optimized packet-switched services. The notation of supporting "data directly overoptics" has been fueled by the promise that elimination of unnecessary network layers willlead to a vast reduction in the cost and complexity of the network.In this view of reduced or collapsed network layers, existing TDM systems such asSynchronous Digital Hierarchy (SDH) plays a diminishing role, and optical transportnetworking emerges as the underlying transport infrastructure for the resultant "networkof networks".Optical InternetOptical internet working, for example, as defined by the Optical Interworking Forum (OIF),is a data-optimized network infrastructure in which switches and routers have integratedoptical interfaces and are directly connected by fiber or optical network elements, such asDense Wavelength-Division Multiplexers (DWDMs).At present, however, the notion of IP directly over WDM is little more than cleverlydisguised marketing. Almost invariably, IP over WDM is IP packets mapped into SDH,coupled with SDH based point-to-point DWDM systems. SDH standalone elements, oftenreferred to as Time-Division Multiplexer (TDMs), are not required, but SDH remains anintegral element of the data networking equipment interface.Ever-increasing reliance on the presence of SDH in DWDM systems limits technologicalinnovation. For example, it may inhibit packet over fiber applications such asAsynchronous Transfer Mode (ATM), Gigabit Ethernet (GbE) and 10 GbE over DWDM. Nordoes it bring us any closer to realizing the ultimate vision of optical transport networking.As compared to the present view of IP over WDM, there is a more balanced view ofdata/transport network evolution. This balanced view is based on two fundamentalprinciples: Every data network is unique, in a marketplace governed by differentiation. The Optical Transport Network (OTN), as the underlying infrastructure "network ofnetworks" should be capable of transporting a wide variety of client signals,independent of their format.Together, these fundamental principles form the basis for the notion of optical datanetworking.1
Optical Networks2. Optical Networks Convergence NetworksToday's TDM-based transport networks have been designed to provide an assured level ofperformance and reliability for the predominant voice and based-line services. Proventechnologies, such as SDH, have been widely deployed, providing high-capacity transport,scalable to gigabit per second rates, for voice and leased-line applications. SDH selfhealing rings enable service-level recovery within tens of milliseconds following networkfailures. All of these features are supported by well-established global standards enablinga high degree of multivendor interoperability.Today’s NetworkIn contrast to today's TDM-based transport networks (and, to some extent, with ATMnetworks), "best-effort" IP networks generally lack the means to guarantee high reliabilityand predictable performance. The best-effort service provided by most legacy IP networks,with unpredictable delay, jitter, and packet loss, is the price paid to achieve maximum linkutilization through statistical multiplexing. Link utilization (e.g. the number of users perunit of bandwidth) has been an important figure of merit for data networks, since the linksare usually carried on leased circuits through the TDM transport network.Given the inherently bursty nature of data traffic, the fixed-bandwidth pipes of TDMtransport may not be an ideally efficient solution. However, this inefficiency hastraditionally been considered of less importance than the network reliability and congestionisolation features of a TDM-based transport network provider.The surging demand for high bandwidth and differentiated data services is now challengingthis dual architecture model of TDM-based transport and best effort packet networks. It isnot cost-effective to extend the usefulness of best-effort networking by over provisioningnetwork bandwidth and keeping the network lightly loaded.Furthermore, this approach cannot always be achieved or guaranteed due to spottydemand growth, and is a particular issue for the network access domain, which is mostsensitive to the economic constraints of underutilized facilities. As a result, in general,data service providers today do not have the network infrastructure support to providecustomer-specific differentiated service guarantees and corresponding service-levelagreements.Next Generation NetworkNext generation network architectures for cost-effective, reliable, and scalable evolutionwill employ both transport networking and enhanced service layers, working together in acomplementary and interoperable fashion. These next-generation networks willdramatically increase, and maximally share, backbone network infrastructure capacity,and provide sophisticated service differentiation for emerging data applications.Transport networking enables the service layers to operate more effectively, freeing themfrom constraints of physical topology to focus on the sufficiently large challenge of meetingservice requirements. Hence, complementing the many service-layer enhancements,optical transport networking will provide a unified, optimized layer of high-capacity, highreliability bandwidth management, and create so-called optical data networking solutionsfor higher capacity data services with guaranteed quality.2
Optical NetworksOptical Transport Networking: A Practical ViewVisions of optical networking have captured the imagination of researchers and networkplanners alike, since the rapid and successful commercialization of WDM. In the originalvision of optical transport networking, a flexible, scalable, and robust transport networkemerges, catering to an expanding variety of client signals with equally varied servicerequirements (flexibility, scalability, and survivability coupled with bit rate and protocolindependence).The promise of a transport infrastructure capable of meeting the burgeoning bandwidthdemands well into this new century, wherein wavelengths replace timeslots as the mediumfor providing reliable transfer of high-bandwidth services across the network, is indeedtantalizing. But what is optical networking? The answer varies widely, and in fact hasevolved over recent years. Early attempts at optical networking focused on opticaltransparency and the design of optically transparent networks on a global scale.Practical SolutionIn the absence of viable "all-optical" solutions more practical solutions for opticalnetworking accommodate the need for opto-electronics to support optical signalregeneration, and optical signal performance monitoring. In what is termed all-opticalnetworking, signals traverse the network entirely in the optical domain, with no form ofopto-electronic processing. This implies that the all signal processing including - signalregeneration, routing, and wavelength interchange - takes place entirely in the opticaldomain.Due to limitations of analog engineering (e.g. limiting factor in a properly designed digitalsystem is an accuracy of the conversion of the original analog message waveform intodigital form) and considering the current state-of-the-art in all-optical processingtechnology, the notion of global or even national all optical networks is not practicallyattainable.In particular, opto-electronic conversion may be required in opto network elements toprevent the accumulation of transmission impairments - impairments that result from suchfactors are fiber chromatic dispersion and nonlinearities, cascading of non-ideal flat-gainamplifiers, optical signal crosstalk, and transmission spectrum narrowing from cascadednon-flat filters. Opto-electronic conversion can also support wavelength interchange,which is currently a challenging feature to realize in the all optical domain.3
Optical NetworksIn short, in the absence of commercially available devices that perform signal regenerationto mitigate impairment accumulation and support wavelength conversion in the all-opticaldomain, some measure of opto-electronic conversion should be expected in near-termpractical optical networking architectures. The resulting optical network architectures canbe characterized by optically transparent (or all-optical) subnetworks, bounded by featureenhanced opto-electronics, as shown in the above figure.Client Signal TransparencyBeyond analog network engineering, practical considerations will continue to govern theultimate realization of the OTN. Paramount among these considerations is the networkoperator's desire for a high degree of client signal transparency within the future transportinfrastructure.What is meant by "Client signal transparency"? Specifically, for the desired set of clientsignals targeted for transport on the OTN, individual mappings are defined for carryingthese signals as payloads of optical channel (OCh) server signals. Signals expected in theOTN include legacy SDH and PDH signals, and packet-based traffic such as InternetProtocol (IP), ATM, GbE and Simple Data Lnk (SDL). Once a client signal has been mappedinto its OCh server signal at the ingress of the OTN, an operator deploying such a networkneed not have detailed knowledge of (or access to) the client signal, until it is dem
optical fibers and their connections in networks. The nature of optical networks along with the recent developments in the Optical and Networking systems using optical sources and devices is also dealt with. Audience This tutorial is designed for learners who have interest in learning the networking concepts using optical sources.
Semiconductor Optical Amplifiers (SOAs) have mainly found application in optical telecommunication networks for optical signal regeneration, wavelength switching or wavelength conversion. The objective of this paper is to report the use of semiconductor optical amplifiers for optical sensing taking into account their optical bistable properties .
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A novel all-optical sampling method based on nonlinear polarization rotation in a semiconductor optical amplifier is proposed. An analog optical signal and an optical clock pulses train are injected into semiconductor optical amplifier simultaneously, and the power of the analog light modulates the intensity of the output optical pulse through
Mar 14, 2005 · Background - Optical Amplifiers zAmplification in optical transmission systems needed to maintain SNR and BER, despite low-loss in fibers. zEarly optical regeneration for optic transmission relied on optical to electron transformation. zAll-optical amplifiers provide optical g
optical networks have been made possible by the optical amplifier. Optical amplifiers can be divided into two classes: optical fibre amplifiers (OFA) and semiconductor optical amplifiers (SOAs). The former has tended to dominate conventional system applications such as in-line amplification used to compensate for fibre losses.
The field of optical communications is moving toward the realization of photonic networks with wavelength division multiplexing (WDM) utilizing the full bandwidth of optical fibers. Conventionally, an erbium-doped fiber amplifier (EDFA) and a semiconductor optical amplifier (SOA) are used for amplifying an optical signal in optical communications.
2. Tunable optical filters 3. ADD-Drop Filters 4. Broadband Optical Amplifiers 5. Optical Cross Connects In addition there are a number of important support components that also must be developed. These include: a. Optical Directional Couplers b. Wavelength Filters c. Optical isolators d. Optical Equalizers e. Polarizers, rotators .
The module scst_user API is de ned in scst_user.h le. 3 IOCTL() functions There are following IOCTL functions aailable.v All of them has one argument. They all, except SCST_USER_REGISTER_DEVICE return 0 for success or -1 in case of error, and errno is set appro-priately. 3.1 SCST_USER_REGISTER_DEVICE
